A differential laser driver for 40 Gbit/s optical communications delivering a 10 mA current swing to a laser modeled as a 50Ω resistance in parallel to a 100 fF capacitance is presented. The circuit employs multiple frequency compensation techniques to achieve very high speed without space-consuming inductors. The driver was implemented in a 180 GHz-f_T,max SiGe BiCMOS technology. Measurements showed 15 dB gain with 26 GHz bandwidth and open eyes up to 50 Gbit/s. The driver's power consumption was only 80 mW making it the fastest and most power efficient of all inductor-free 40 Gbit/s SiGe laser drivers published to date.